Control apparatus for internal combustion engine

Abstract

Provided is a control apparatus for an internal combustion engine which can successfully determine whether or not a failure concerning a stopping operation of an exhaust valve has occurred, without the need of providing a dedicated sensor for the failure determination. An intake variable valve operating apparatus ( 62 ) and an exhaust variable valve operating apparatus ( 64 ) are included that have valve stop mechanisms capable of switching each operational state of an intake valve ( 58 ) and an exhaust valve ( 60 ) between a valve operating state and a valve closed/stopped state. It is determined whether or not a failure concerning a stopping operation of the exhaust valve ( 60 ) from the valve operating state to the valve closed/stopped state has occurred, on the basis of the magnitude of the negative torque of when an execution request that is accompanied by a valve stop request to switch each operational state of the intake valve ( 58 ) and the exhaust valve ( 60 ) from the valve operating state to the valve closed/stopped state has been issued, in a case in which it is determined that a failure concerning the stopping operation of the intake valve ( 58 ) has not occurred.

The invention claimed is: 
     
       1. A control apparatus for an internal combustion engine, comprising:
 a valve stop mechanism that is capable of switching each operational state of an intake valve and an exhaust valve between a valve operating state and a valve closed/stopped state; and 
 a controller that is configured to: 
 determine whether or not a failure concerning a stopping operation of the intake valve from the valve operating state to the valve closed/stopped state has occurred; 
 obtain a negative torque of an internal combustion engine; and 
 determine whether or not a failure concerning a stopping operation of the exhaust valve from the valve operating state to the valve closed/stopped state has occurred, on a basis of a magnitude of the negative torque of when an execution request for a fuel cut that is accompanied by a valve stop request to switch each operational state of the intake valve and the exhaust valve from the valve operating state to the valve closed/stopped state has been issued, in a case in which it is determined that a failure concerning the stopping operation of the intake valve has not occurred, 
 wherein the controller determines that a failure concerning the stopping operation of the exhaust valve has occurred, when a torque difference of a current negative torque, with respect to a negative torque of the internal combustion engine in a case in which each stopping operation of the intake valve and the exhaust valve from the valve operating state to the valve closed/stopped state has been normally performed, is a minus value, and when an absolute value of the torque difference is larger than or equal to a predetermined first determination value, 
 wherein the controller is further configured to obtain an engine speed fluctuation or a torque fluctuation of the internal combustion engine, and 
 wherein the controller determines that a failure concerning the stopping operation of the exhaust valve has occurred, when the engine speed fluctuation or the torque fluctuation is larger than a predetermined second determination value, in a case in which the torque difference is a minus value and the absolute value of the torque difference is smaller than the first determination value. 
 
     
     
       2. The control apparatus for an internal combustion engine according to  claim 1 ,
 wherein the controller is further configured to obtain an engine rotational acceleration, and 
 wherein the controller performs a determination as to whether or not a failure concerning the stopping operation of the exhaust valve has occurred, when the absolute value of the engine rotational acceleration is smaller than a predetermined third determination value. 
 
     
     
       3. The control apparatus for an internal combustion engine according to  claim 1 ,
 wherein the controller determines that the number of cylinders in which a failure concerning the stopping operation of the exhaust valve has occurred is larger in a case in which the torque difference is large on a minus side as compared with a case in which the torque difference is small on the minus side. 
 
     
     
       4. A control apparatus for an internal combustion engine, comprising:
 a valve stop mechanism that is capable of switching each operational state of an intake valve and an exhaust valve between a valve operating state and a valve closed/stopped state; 
 intake valve failure determination means for determining whether or not a failure concerning a stopping operation of the intake valve from the valve operating state to the valve closed/stopped state has occurred; 
 negative torque obtaining means for obtaining a negative torque of an internal combustion engine; and 
 exhaust valve failure determination means for determining whether or not a failure concerning a stopping operation of the exhaust valve from the valve operating state to the valve closed/stopped state has occurred, on a basis of a magnitude of the negative torque of when an execution request for a fuel cut that is accompanied by a valve stop request to switch each operational state of the intake valve and the exhaust valve from the valve operating state to the valve closed/stopped state has been issued, in a case in which it is determined that a failure concerning the stopping operation of the intake valve has not occurred, 
 wherein the exhaust valve failure determination means determines that a failure concerning the stopping operation of the exhaust valve has occurred, when a torque difference of a current negative torque, with respect to a negative torque of the internal combustion engine in a case in which each stopping operation of the intake valve and the exhaust valve from the valve operating state to the valve closed/stopped state has been normally performed, is a minus value, and when an absolute value of the torque difference is larger than or equal to a predetermined first determination value, 
 wherein the control apparatus for the internal combustion engine further includes engine fluctuation obtaining means for obtaining an engine speed fluctuation or a torque fluctuation of the internal combustion engine, and 
 wherein the exhaust valve failure determination means determines that a failure concerning the stopping operation of the exhaust valve has occurred, when the engine speed fluctuation or the torque fluctuation is larger than a predetermined second determination value, in a case in which the torque difference is a minus value and the absolute value of the torque difference is smaller than the first determination value.